Building Tech: Metals & Joining Methods

• Building Technology I, Division 05 covers metals

Types of Metals

• Aluminum
• Iron
• Steel
• Copper
• Tin
• Zinc
• Brass
• Bronze
• Chromium
• Nickel
• Lead

Methods of Joining Metals

• Soldering
• Brazing
• Welding
• Rivets

Metals for Concrete Reinforcement.

• Steel Bars
• Wire Fabric
• Expanded Mesh
• Laths

Storage and Care for Metal Reinforcement

Aluminum

• A soft, nonmagnetic, silvery metal
• Light weight (1/3 of iron, brass, or copper)
• Low melting point
• High thermal and electrical conductivity, surpassed only by silver and copper
• Moderately high coefficient of expansion
• Combines with oxygen to form aluminum oxide, a transparent corrosion-resistant film
• Attacked by alkalis, hydrochloric acid, and other dilute acids
• Subject to galvanic action, requiring electrical insulation from other metals
• Easily worked by hot or cold rolling, extrusion, forging, pressing, drawing, molding, stamping, bending, and shaping
• Can be riveted, bolted, welded, brazed, and soldered

Aluminum in Architecture

• All fabricated forms are used
• These forms include rod, bar, extrusion, casting, sheet, and strip
• Extrusion shapes material by forcing it through a shaped opening in a die
• These products are often alloyed with iron, silicon, copper, manganese, magnesium, zinc, chromium and nickel for strength, potentially reducing corrosion resistance

Alclad Aluminum

• A protective coating primarily for corrosion resistance
• It is applied to thin sheets of an alloy whose corrosion resistance has been decreased by added strengthening constituents
• Cladding improves alloy appearance
• It usually consists of pure aluminum, magnesium silicide, or zinc alloys, with or without manganese

Types of Aluminum

• Aluminum Sheet and Strip are used for roofing, flashing, and gutters
• Aluminum Foil is rolled to a 0.005" thickness and is used for thermal insulation and vapor barriers
• Corrugated Aluminum sheet is rigidized and fabricated for roofing and siding using alloys with high corrosion resistance
• Structural Aluminum: Aluminum is extruded to meet structural design needs, and available alloys are corrosion resistant, and require no painting, allowing for reduced thickness
• Aluminum is very lightweight to allow increased efficiency with large bay spacing for aluminum girders and columns and buckling should be checked
• Aluminum Doors and Windows: Generally fabricated from extrusions and rolled shapes
• Aluminum Panels and Sandwich Panels: prefabricated units are manufactured using dimensions of modular and non-modular window-width, using 600mm, 900mm, and 1200mm widths for interior partitions and dividers
• Panels for the exterior of buildings primarily consist of an aluminum exterior facing, which may be an aluminum casting,or an extrusion or sheet material pressed, stamped or formed into specially design shapes
• A sandwich panel comprises a system of construction called skin construction and has cellular core of aluminum on both sides
• Ornamental aluminum includes rods, bars, pipes, railings, fittings, and special shapes manufactured as stock items for use in ornamental designs for railings, grilles, screens, etc
• Aluminum mesh and wire cloth are used for fencing, particularly chain link fencing, and also for insect screening

Aluminum Finishes

• Mechanical finishes are achieved by grinding, polishing, scratching, sandblasting, or embossing
• Chemical finishes modify the aluminum surface and permit only limited colors:
  • Etching, cleaning, or polishing to remove oxide film and create a clean/polished surface
  • Oxidizing with metallic oxides to protect the surface;
• Electrolytic finishes (anodized) develops a protective oxide coating, for specific aluminum capabilities
  • The coating can be transparent or opaque and absorb dyes
  • Architectural gold is the most stable color, while blue, brown, and black are also available
• Electroplating applies a protective or decorative film of another metal
  • In the case of copper and nickel, the coating must be complete to avoid galvanic action
• Porcelain or Vitreous Enamel forms a hard, resistant surface, available in a broad, glassy color range
• Paint (lacquer and enamel) requires aluminum surface preparation and shouldn't be lead-based

Iron

• Pure iron is tough, malleable, silvery-white metal and is easily magnetized
• It is also soft and ductile, oxidizing rapidly in air and is attacked by most acids
• Iron can be hardened by heating and sudden cooling
• It is made more pliable or more workable by heating and slow cooling
• Brittle at very low temperatures
• Soft at red heat
• Weldable at white heat
• As pure iron passes through temperature ranges, it undergoes changes in its structure and properties
• The commercial form in which iron is first prepared is crude, or pig iron which contains 3-4% carbon
• Pig iron and varying amounts of silicon, sulfur, phosphorous and managanese is the starting point for all other forms of iron and iron alloys (or steel) that are produced
• The key to the range of types of iron and steel is the carbon-iron relationship

Cast Iron

• An iron-carbon alloy that contains more than 1.7% carbon
• Poured while molten into forms
• Easily cast into any shape, but is too hard and brittle to be shaped by hammering, rolling, or pressing
• Utilized in architecture for piping and fittings, enameled plumbing fixtures and miscellanous castings
• Two types of cast iron often used are gray cast iron and malleable cast iron with heavy use in heavy machinery and industry
• These cast irons have significant compressive strength coupled with capacity to absorb energy and stop vibration

Wrought Iron

• Almost pure iron with less than 0.1% carbon (usually <0.05%)
• Contains 2.5% of slag (iron silicate)
• The 2.5% of slag in wrought iron is purely physical as not alloyed
• Characterized as soft, malleable, tough, fatigue-resistant, and resistant to progressive corrosion
• Demonstrated good machinability and can endure forging, bending, rolling, drawing, and spinning, with any welding processes supported
• Comes available in the form of pipes, plates, sheets, special shapes, and bars
• Wrought iron is used in architecture, typically in the form of pipes, chains, sheets, and ornamental ironwork: Plumbing, heating, and air conditioning make use of wrought iron’s corrosion-resistant and durable characteristics
• Requires highly skilled craftsmanship due to its relationship with classical architecture
• Employed particularly in furniture, railing, fences, grilles, and small decorative objects

Steel

• Steel refers to plain carbon steels which are defined as alloys containing iron and carbon
• Carbon content can not exceed 2% carbon and are made in malleable or ingot form
• Iron exceeds 95% of the composition of straight or plain carbon steels
• Phosphorus, sulfur, oxygen and nitrogen are also present, though the last 3 are impurities
• Manganese, silicon, aluminum, copper and nickel may also be present as deliberate additions or residual impurities to control the steel properties
• Steel can be wrought, rolled, cast, and welded, by can not be extruded

Wrought Carbon Steels

• Structural steel is a medium carbon steel with controlled carbon content for strength and ductility
  • Structural steel is available in angles, channels, I-beams, H columns, T shapes, Z shapes, plates, round pipe columns, sheet piling, open web joists, and light steel framing shapes.
• Reinforcement of concrete uses deformed bars of several different grades and diameters
• Sheet and strip steel are made containing about 0.15% carbon and not exceeding 0.25%
  • Strip by definition is a sheet material that is 12" or less wide.
  • It is used in fabricated form as decking galvanized sheet, expanded metal, panels and sandwich panels, and as a base metal for porcelain enamel.
• Corrugated steel is rigidized, fabricated from low-carbon, cold or hot-rolled sheet with galvanization or bituminous coating
• If galvanized has a silvery sheen and glittering frosted surface and commonly comes in 18, 20, 22, 24, and 26 gauge sheet and strip
• Steel Mesh and Wire Cloth are used for reinforcing concrete, lath for plaster, stucco, and cement, fencing, and insect screens
• Steel Windows and Doors
• Hardware such as nails, screws, rivets, etc

Alloy Steels

• Steels combine alloys (manganese, silicon, aluminum, titanium, and molybdenum) in sufficient quantity to produce properties unobtainable in carbon steels
• The alloying elements are added to increase properties like:
  • Strength
  • Hardness
  • Hardenability
  • Performance at high-low temperatures
  • Electromagnetic properties
  • Wear Resistance
  • Electrical Conductivity In structural applications, of particular interest to architects the properties of strength, expansion, resistance to corrosion, ductility, and workability
• High-strength low-alloy steels offer improved mechanics and resistance to atmospheric corrosion
  • Increasingly used for pre-stressed concrete reinforcement, high strength bolts, special structural steels and cables for elevators, etc.
• Stainless steel is used in architecture as a highly alloyed steel with more than 10% chromium, in response to its corrosion and heat resistance
  • Stainless stells generally see use corrosion resistance, durability, and minimum maintenance are a must
  • It is commonly found in exterior and interior wall finishes, doors, windows, trims, railings, signs and letters, appliances, etc.

Copper

• ductile, malleable, nonmagnetic metal with a bright, reddish-brown color
• has high electrical and thermal conductivity (second to Silver)
• Copper useful alloys have enough strength minor structural work, and easily worked
• It is attacked by alkalis and many common acids
• Resistant to corrosion by air and salt water
• On exposure, copper surface forms an insoluble green salt that prevents more corrosion
  • The green color is known as its "patina"
• Copper can be cast, drawn, extruded, hot and cold worked, spun, hammered, punched, welded, brazed and soldered
• Galvanic action must be evaluated during copper usage in architecture: should metal and and electrolyte contact each other, the assembly could corrode

General Info on Copper

• The copper itself, being cathode does not corrode
• Copper is one of electrical conductors commonly found in wires and bus bars
• Copper sheet and strip are commonly found in roofing and flashing

Tin

• soft, ductile, malleable, bluish-white metal
• Because of thin film of stannic oxide, tin resists corrosion due to air, sulfur-dioxide, moisture, and hydrogen sulfide
• Takes a highly reflective polish and able to wet other metals with a thin film of stannic oxide, to resist corrosion
• Tin is primarily of use for protective coatings of stronger metals
• Architectural applications include bronzes, brasses, terneplate, mirrors, gilding, solders, hardware and fusible alloys.

Zinc

• A medium-hard, bluish-white metal
• Characterized via brittleness and low strength
• Readily attacked by acids and alkalis.
• Zinc is resistant to water corrosion
• The film of zinc carbonate or zinc oxide can protect against further oxidation
• Commonly used as die-casting metal for alloy element in brasses as a protective coating via galvanizing
• Galvanization protects steel and iron from corrosion
  • Galvanizing's advantage stems from, in the event of iron-steel exposure due deterioration, galvanic reaction between the coating and the base metal happens, with zinc corroding against further iron-steel destruction.
• Galvanized architecture may become discolored when subjected to excess dampness and/or heat as zinc hydroxide can be formed, thus destroying the galvanizing

Brass

• An alloy of copper and zinc with small percentages of other elements to add special qualities.
• The copper-zinc proportions range from 95% copper to 5% zinc up to 55% copper to 45% zinc.
• Brass alloys are less hard and strong than steels, however, more preferable in the qualities of workability and resistance to corrosion.
• All brasses react with other metals; the brass' galvanic series-position should be reviewed
• Galvanic interactions ensue at contact between iron, steel or stainless, zinc, aluminum, magnesium should an electrolyte be present
• Brasses primarily serve doors, window/door/window frames, and for ornamental metalwork (railings, trims, grilles)
• Brasses are extensively in hardware/plating and miscellanous units, for example screws, bolts, nuts/anchors

Bronze

• Is an alloy of copper and tin
• Varies only slightly from 90% copper and 10% tin composition
• A rich, golden-brown metal that can endure corrosion
• Originally used for forging, bronze offers best properties for easy casting, due to its dense and hard properties, allowing any sensitive mold-impression
• “Bronze” is no longer used in its limited sense.
• “Brass” and “Bronze” are interchangeable commercial practice
• “Bronze” now has a prefix and indicates alloys of copper with silicon, manganese, aluminum, and other elements with or without zinc
• Some brasses are bronzes because they have the bronze color.
• Statuary bronze (97% copper, 2% tin and 1% zinc) is a bronze in architectural applications
• Commercial bronze and architectural bronze are leadded brass
• The architectural uses of bronze are limited to statues, plaques, medallions, and other ornamentation and rough and finish hardware

Chromium

• A steel-white metal that takes a brilliant polish, harder than cobalt or nickel.
• It is nonmagnetic at ordinary temperatures, however, becomes magnetic at 13°F
• Does not tarnish in air, resists oxidizing agents, but soluble in acids and strong alkalis
• Its use is an alloying ingredient in ferrous and nonferrous metallurgy
• Chrome plating is one of most encountered use of this material in architecture, featuring a thin, hard, bright resistant surface which discharges water when highly polished
  • Metals like chrome alluminum, iron, copper, titanium and zinc are fit with an electro-deposited chromium thin coat metal.

Nickel

• An inert, silvery metal that is resistant to strong alkalis and acids.
• Nickel is related to iron in strength and to copper for its oxidation resistance.
• It is malleable and can undergo forging, bending, rolling, intrusion and spinning.
• Nickel applications imparts qualities like ductility, strength and corrosion-resistance at heightened temperatures when combined with metal for greater functionality
• It is mainly an alloy-material

Lead

• blue-gray, soft, very heavy, workable metal able to recover from various processes
• Relatively impenetrable in radiation
• Metallic lead offers with various solutions for corrosion resistance
• Applications involve pipe, wire and rolled material
• Serves expansive item uses, for instance bolts in masonry and lead-head nails

Methods of Joining Metals

Soldering

• Seals with lower melting solder
• Temperature does not encourage bonding
• • Soldered joints contain no capacity for tensile strength
• Three major types
  • Tin-Lead - general purpose -Lead-Antimony
  • Silver-Lead
• Preexisting can be applied

Metal Bath Dip Soldering:

• Metal connection via submerging part in molten solder (350 to 600˚F), adhesion of object and joining metal happens A cleaner is in use for preparation and an automated type is commonly deployed

Soldering With Iron

• Preheated and joined with solder, a type of substrate, with intense heat to form the connection using an iron instrument

Using Torch

• Areas must be heat-applied before the deployment of solder, but usage is restricted to certain qualities-retaining metals

Sweat Method

• Involves heat to fuse materials
• Works when joining copper tubes and units
• Fluxes
• Acid-type
• Salt chlorides such as magnesium and other metals, demanding a cleansing process due to corrosiveness and electrictivity-related applications

Neutral Fluxes

• Stearic acid for metal, brass, lead and tin plate
• Mild

Noncorrosive

• Non-resistance, requiring no removal of Rosin, or its flux type

Brazing

• An operation to solder that deploys warmer temperatures
• A combination of elevated-bond/molten metals to fill joints
• Interlinkages happen between the part and molten source
• Brazing is effective on areas that need resistance from tension because of heat alteration
• These categories commonly include various zinc metal
• Aluminum-silicon
• All involve heat-opposing substances

Welding

• Unites bonds of metals via heat
• Deployment ranges
  • Connection/ Heat, pressure and molten metals
  • Joints become as if not greater than the part
  • 5500˚F needed of heat
  • Electrode use involves metal and parts of electric deployment for great functionality

Rivets

• Joins via material tie
• Cylinder that is flattened end, and connects into various substances

Metals for Concrete Reinforcement

Steel Bars

• Metal deployment of reinforcement via:
• Metals forged to better link the set cement
• Billets
  • Bessemer heating usage with 3 grades.
  • Steel forged to enhance build with various strengths
  • Steel bars can vary at 29-inches height and 20/30 -inch length

Wire Fabric

• Deployment of steel wiring for reinforcement via:
  • Metal deployment from low heat. Cold

Welded Build

- Metal deployment with a grid
- Metal grade can be 50-240 inches in diameter and 67-200 inches in length

Traingle-mesh Build

• With single-strand wiring and 4 inches from parts for reinforced functionality

Expanded Mesh

• Formed through cutting and piercing a pattern into a solid metal sheet, and is often stamped. and used for creating an open mesh devoid of mechanical and welded elements

Laths

• Permanent centering or self-centering are often constructed in many shapes featuring segments, or level-material sheets
• It can act as an open-mesh type with zinc and copper alloys

Storage and Care for Metal Reinforcement

• Metal reinforcements must be situated on racks distant as possible from dampness, with sheds situated overhead
• However, rust indicates that the scaling is reducing the cross section ability
• Rust reduces bond across alloy with use and deployment is restricted where alloys are exposed to an outside type of application